I have a question regarding the more like this query Currently, I'm making
a solution to match "more like this" product based on its tags.id . I have
the _mapping of product which is something like this :

{
name(:string),
tags: [ {id(:integer}, {id(:integer)} ]
}

I have tried something like this :elasticsearch:9200/<index_name>/product/_mlt?mlt_fields=tags.id but it
doesn't seem to work. I got the error :
{"error":"NumberFormatException[For input string: "[67773, 71354, 68265,
70599, 81670, 191917]"]","status":500}

Elasticsearch doesn't work automagically which is great. But I'm not clear
what is problem I have and what is a good way to solve this problem.

not sure on the top of my head, but I think, MLT queries need an analyzer,
which creates char terms - where as numeric analyzers in lucene do not.
This is the reason why MLT does not work with numbers. In your case a
workaround might be easy, by just indexing the real tagnames and search for
documents with the same tag (maybe you do not need MLT then).

I have a question regarding the more like this query Currently, I'm making
a solution to match "more like this" product based on its tags.id . I
have the _mapping of product which is something like this :

{
name(:string),
tags: [ {id(:integer}, {id(:integer)} ]
}

I have tried something like this :elasticsearch:9200/<index_**name>/product/_mlt?mlt_fields=**tags.idhttp://tags.id/ but
it doesn't seem to work. I got the error :
{"error":"**NumberFormatException[For input string: "[67773, 71354,
68265, 70599, 81670, 191917]"]","status":500}

Elasticsearch doesn't work automagically which is great. But I'm not clear
what is problem I have and what is a good way to solve this problem.